The present invention concerns a new and useful rail assembly for transmitting electrical current to a trolley or similar vehicle making contact with the rail assembly.
Known current-conducting rail assemblies usually include a base member and an attached contact member formed of a highly wear-resistant material, such as steel. In one known assembly, a base member has a dual T-shaped profile and is formed of a light-weight alloy, such as aluminum. A flat steel band is attached to the base and serves as a contact track for the trolley. Because the trolley is not guided by the flat track, there exists the constant danger of the trolley separating from the contact track.
A basic problem confronting dual T-shaped rail assemblies is a phenomenon known as the "skin effect", which relates to movement of alternating current along the surface of the rail conductor. As a result, the effective area or profile actually transmitting the alternating current therethrough is substantially reduced. This shows as an apparent increase in the ohmic resistance of the conductor to alternating current, resulting in a reduced operating efficiency of the rail conductor. A further indication of the reduced efficiency is the ratio of the total cross-sectional area of the conductor to the electrical load capacity for alternating current.
In an effort to overcome these problems, a V-shaped contact track has been developed for use with a trolley having a corresponding contour. Because the V-shaped contact track must be wear resistant, it has been necessary to form the entire contact track from steel, greatly increasing the overall expense of the rail assembly without any appreciable increase in the operating efficiency.
As will be discussed in detail hereafter, applicant's new and useful invention solves the problems confronting the dual T-shaped rail assemblies without the extra expense of an extirely V-shaped steel contact track. In particular, the present invention includes a pair of non-linear support rails formed of a light-weight alloy, such as aluminum, with each curved rail supporting a flat contact band formed of a highly wear-resistant material, such as steel.
As a result, the present invention manages to increase the alternating current load capacity with a reduced profile area, while maintaining the mechanical strength of the assembly.